Taper-locked adjustable connector

ABSTRACT

A connection assembly between a spinal implant rod and a vertebral anchor. The assembly has a longitudinal member, a housing, a rod interface washer, and a compression member. The longitudinal member has an aperture at one end and a wedge at the other. The housing has a passageway to accept the shank of a bone screw and a bore to accept the wedge. The bore is open to the passageway so that when the wedge is pulled from the bore it pushes against the shank of the bone screw, trapping the bone screw between the wedge and the sidewalls of the passageway. Threading a setscrew into the aperture presses a spinal rod against the washer, presses the washer against the housing, and pulls the wedge against the shank of the bone screw. Further tightening of the setscrew then locks the bone screw and rod together.

This invention relates to a connection between a spinal rod and avertebral anchor with a tapered locking surface that traps the vertebralanchor in the connection fitting.

BACKGROUND OF THE INVENTION

Spinal implant systems provide a rod for supporting the spine and forproperly positioning components of the spine for various treatmentpurposes. Bolts, screws, and hooks are typically secured to thevertebrae for connection to the supporting rod. These vertebral anchorsmust frequently be positioned at various angles due the anatomicalstructure of the patient, the physiological problem being treated, andthe preference of the physician. It is difficult to provide secureconnections between the spinal support rod and these vertebral anchorsat all the various angles and elevations that are required, especiallywhere there are different distances between the rod and bolts and wherethese components are located at different heights on the patient.

What is needed is a connection assembly between a spinal rod and avertebral anchor that allows the surgeon to fix the desired elevationbetween a rod and the bone anchor as well as fix the desired anglebetween the anchor and rod. The following invention is one solution tothat need.

SUMMARY OF THE INVENTION

In one aspect, this invention is a connection assembly between a spinalimplant rod and a vertebral anchor. The connection assembly includes alongitudinal member with a friction shoe at one end and an aperture atthe other. The connection assembly also includes a housing. The housinghas a passageway to receive a portion of the vertebral anchor and a boreto receive at least a portion of the shoe of the longitudinal member.The housing also includes a rod interface washer. The washer ispositioned over the longitudinal member between the aperture of thelongitudinal member and the face of the housing. The connection assemblyfurther includes a compression member. The compression member isforceably, for example threadably, engageable into the aperture of thelongitudinal member to urge the rod toward the vertebral anchor, wherebythe shoe will be moved in the bore to urge the vertebral anchor towardthe internal wall of the passageway in the housing, further pressing thehousing and said rod interface washer together.

As used in this specification the term “shoe” means a structure thatretards, stops, or controls the motion of another structure. WEBSTER'SNINTH NEW COLLEGIATE DICTIONARY 1088 (1990).

BREIF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of one embodiment of the present invention.

FIGS. 2 and 2A are top plan views of first and second embodiments of theinvention.

FIGS. 3 and 3A are side elevational views of first and secondembodiments of the invention.

FIGS. 4 and 4A are side cross-sectional views of first and secondembodiments of the invention.

FIGS. 5 and 5A are top plan views of a longitudinal member used in firstand second embodiments of the invention.

FIGS. 6 and 6A are side elevational views of a longitudinal member usedin first and second embodiments of the invention.

FIGS. 7 and 7A are side cross-sectional views of a longitudinal memberused in first and second embodiments of the invention.

FIGS. 8 and 8A are end views of a longitudinal member used in first andsecond embodiments of the invention.

FIGS. 9 and 9A are top cross-sectional views of a housing used in firstand second embodiments of the invention.

FIGS. 10 and 10A are bottom plan views of a housing used in first andsecond embodiments of the invention.

FIGS. 11 and 11A are axial cross-sectional views of a housing used infirst and second embodiments of the invention.

FIGS. 12 and 12A are end elevational views of a housing used in firstand second embodiments of the invention.

FIGS. 13 and 13A are bottom plan views of a rod interface washer used infirst and second embodiments of the invention.

FIGS. 14 and 14A are side views of a rod interface washer used in firstand second embodiments of the invention.

FIGS. 15 and 15A are end views of a rod interface washer used in firstand second embodiments of the invention.

FIGS. 16 and 16A are perspective views of a longitudinal member and rodinterface washer used in first and second embodiments of the invention.

FIGS. 17 and 18 are perspective views of an embodiment of the invention.

FIGS. 19 and 20 are plan views of an embodiment of the invention.

FIGS. 21, 22 and 23 are respectively top, side and end views of alongitudinal member used in one embodiment of the invention.

FIGS. 24, 25 and 26 are respectively top, end and side views of ahousing used in one embodiment of the invention.

FIG. 27 is a perspective view of one embodiment of the invention.

FIG. 28 is a perspective view of a spindle used in one embodiment of theinvention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Specific language is used in the following description to publiclydisclose the invention and to convey its principles to others. No limitson the breadth of the patent rights based simply on using specificlanguage are intended. Also included are any alterations andmodifications to the description that should normally occur to one ofaverage skill in this technology.

A connection assembly 1 according to one embodiment of the invention isshown in FIGS. 1 to 4, and another embodiment of the invention is shownin FIGS. 2A to 4A. In either embodiment, connection assembly 1 includesa longitudinal member 2, a housing 3, and a rod interface washer 4.Longitudinal member 2 has an aperture 6 for receiving a rod “A” in aspinal implant system. While a closed aperture is shown, it willnevertheless be understood that an open-sided aperture may also be usedto permit top-loading of the rod. And structure for urging the rodwithin the aperture 6, such as the set screw 5, is provided through asuitable threaded opening 7 in the longitudinal member 2 so as to beextendable into the aperture 6. The housing 3 has a passageway 8 forreceiving a shaft or shank of a vertebral anchor “B” of a spinal implantsystem. Here again, while a closed passageway is shown, it willnevertheless be understood that an open-sided passageway may also beused.

Additional details of longitudinal member 2 are shown in FIGS. 5 to 8for one embodiment, and 5A to 8A for a second embodiment. Longitudinalmember 2 has a friction shoe 9 near end 10. Friction shoe 9 has aninwardly tapered seat surface 11 that generally widens from neck portion12 over the length of tapered seat surface 11 toward end 10. In FIGS. 5to 7, the profile of tapered seat surface 11 is shown as generallyconvex our bulbous 15, however, other profiles are also contemplated bythis invention. The practitioner of this invention may also use aninwardly tapered seat surface 11 with a generally concave profile 13(dashed line in FIGS. 5 or 5A), which may, for example, resemble theprofile of the flared bell on a trumpet. Or, the practitioner may use atapered seat surface 11 with a generally straight profile 15A as shownFIGS. 5A to 7A or 15B in FIGS. 21 and 22. Above neck portion 12,longitudinal member 2 has a washer seat portion 14. A washer seatportion 14 that is substantially rectangular in cross-section,optionally with rounded corners, is currently preferred, but washer seatportion 14 can largely be of any suitable shape. Above washer seatportion 14, longitudinal member 2 has a washer stop surface 16. Washerstop surface 16 can be provided in longitudinal member 2, as shown, byproviding an enlarged portion of the longitudinal member 2 next towasher seat portion 14.

Additional details of housing 3 are shown in FIGS. 9 to 12 for oneembodiment, and FIGS. 9A to 12A for a second embodiment. Housing 3 canbe any of several suitable shapes, including the general round shapedepicted in FIG. 10 or the general “D”-shape depicted in FIG. 10A.Housing 3 has a passageway 8 in its lateral edge 23 that is open betweenthe top 24 of housing 3 and the bottom 25 of housing 3. Passageway 8 issized to accept the shank of a vertebral anchor. Housing 3 also has abore 17 that is preferably open between faces 21 and 22 of housing 3.Bore 17 is sized to accept the frictional shoe 9 of longitudinal member2. Bore 17 is open to passageway 8 along radius 18, such that the shaftof vertebral anchor “B” placed inside passageway 8 partially extendsinto bore 17. One face of housing 3 has a washer connection surface 19.Washer connection surface 19 preferably includes structure forfacilitating the engagement of housing 3 against rotational movementrelative to the rod interface washer 4 against which it is pressed. Thisengagement structure is preferably a plurality of variable angle ridges20 that radiate from the axis 31 of bore 17.

Details of rod interface washer 4 are shown in FIGS. 13 to 14 for oneembodiment and FIGS. 13A to 14A for a second embodiment. The interfacewasher can be any of several suitable shapes, including the circularshapes that are depicted. One surface of rod interface washer 4 has anengagement surface 26, which preferably has an engagement groove 27 forengaging a cylindrical rod. The engagement groove 27 runs substantiallydiametrically through the washer. A central opening 28 in the washercorresponds in shape to the cross-sectional shape of the washer seat 14of longitudinal member 2 to which it is engaged (FIG. 16 and FIG. 16A).In the currently preferred embodiments, the corresponding openings andwasher seats are of substantially rectangular shape, although the actualshape and size could vary.

The rod interface washer 4 has a housing connection surface 29 oppositethe engagement surface 27. The housing connection surface 29 preferablyincludes structure for facilitating the engagement of the washer againstrotational movement relative to the housing 3 against which it ispressed. This engagement structure is preferably a plurality of variableangle ridges 30, which radiate from the rotational center of the rodinterface washer 4.

The rotable connection assembly and its manner of assembly are shown incross-section in FIG. 4 for one embodiment and FIG. 4A for a secondembodiment. A rod “A” is positioned in the aperture 6 of longitudinalmember 2. The post or shaft of a vertebral anchor “B” is positionedthrough passageway 8 of housing 3. It will be appreciated that thevertebral anchor “B” is typically oriented somewhat vertically into thespine when the patient is lying horizontally, and that the rod “A”extends somewhat horizontally along the length of spine of the patient,again when the patient is lying.

Housing 3 and rod interface washer 4 are positioned on longitudinalmember 2. Rod interface washer 4 rides over washer seat portion 14 oflongitudinal member 2 (FIGS. 16 and 16A) and shoe 9 is inserted insidebore 17 of housing 3. The housing connection surface 29 of rod interfacewasher 4 faces the washer connection surface 19 of housing 3 in thecompleted assembly, which allows the variable angle surfaces 20 and 30to be placed together, permitting mutual engagement of the two surfaces.

Longitudinal member 2 is generally held in housing 2 by the insertion ofthe shank of a vertebral anchor “B” into passageway 8. When the shank isinserted into passageway 8, the frictional shoe 9 can no longer beremoved from bore 17. A portion of the shank extends into bore 17between end 10 and aperture 6, and pulling longitudinal member out ofbore 17 places inwardly tapered seat surface 11 in contact with theshank of vertebral anchor “B”, preventing longitudinal member 2 frombeing further removed.

As a result of this arrangement, connection assembly 1 may be tightenedto rod “A” and vertebral anchor “B” by threading compression member 5into threaded opening 7. Threading compression member 5 into opening 7clamps rod “A” between rod interface washer 4 and compression member 5.This action, in turn, interlocks connection surfaces 19 and 29 and pullsfrictional shoe 9 from bore 17. Pulling frictional shoe 9 from bore 17clamps the shank of vertebral anchor “B” between the side wall ofpassageway 8 and the inwardly tapered seat surface 11 of shoe 9, lockingthe entire connection assembly against movement. Adjustments are thenmade loosening set screw 5 and then retightening the set screw when thepreferred position has been located.

Several details should now be noted. First, the width of housing 3 androd interface washer 4 is such that when connection assembly 1 isloaded, but not tightened, onto a rod and vertebral anchor, there issome freedom of movement of housing 3 and washer 4 over longitudinalmember 2. And preferably, this freedom of movement is sufficient toallow washer connection surface 19 and housing connection surface 29 toslide past each other. Second, the aperture 6 of longitudinal member 2and passageway 8 of housing 3 are larger in dimension than thecross-section of the rod “A” or vertebral anchor “B”, such that movementof each within their respective openings is possible. And third, it isgenerally preferable that washer seat portion 14 be of sufficient lengthand width to ride on bore 17 when connection assembly has not yet beentightened to a rod and vertebral anchor. In some applications, this mayincrease the ease with which connection assembly 1 can be tightened.

So being, the connection assembly 1 can be readily located most anywhereon a spinal rod, can be readily located most anywhere over the shank ofa vertebral anchor, and connection assembly 1 can accommodate most anyangle between the rod and the vertebral anchor. Additional details ofthe installation of such vertebral anchors and advantages of suchmultiple adjustments in the X, Y, and Z planes can be found in U.S. Pat.Nos. 5,643,263 and 5,885,285 to Simonson, the disclosures of which beingspecifically incorporated into this specification by reference.

Yet another alternative embodiment of connection assembly 1 is shown inFIG. 17. As with the previous embodiments and referring to FIG. 18, thisversion also includes a longitudinal member 2, a housing 3, and a rodinterface washer 4. This embodiment, however, has an elongatedpassageway 8, which allows the surgeon to variably fix the distancebetween vertebral anchor “B” and a rod residing in aperture 6. CompareFIGS. 19 and 20. Vertebral anchor “B” can be clamped in passageway 8near end 32, can be clamped in passageway 8 near end 33, or anchor “B”can be clamped in passageway 8 at any location between ends 32 and 33.

Additional details of longitudinal member 2 of this embodiment are shownin FIGS. 21 to 23. Again, longitudinal member 2 has an aperture 6 forreceiving a spinal implant rod and a threaded opening 7 for receiving asetscrew. And also again, longitudinal member 2 has a friction shoe 9near end 10. Friction shoe 9 has an inwardly tapered seat surface 11that generally widens from neck portion 12 over the length of taperedseat surface 11 toward end 10. In FIGS. 21 to 23, the profile of taperedseat surface 11 has a generally straight profile 15B, however, thisembodiment may also incorporate the previously described convex orconcave profiles. Above neck portion 12, longitudinal member 2 has awasher seat portion 14. A washer seat portion 14 that is substantiallyrectangular in cross-section, optionally with rounded corners, iscurrently preferred, but washer seat portion 14 can largely be of anysuitable shape. Above washer seat portion 14, longitudinal member 2 hasa washer stop surface 16. Washer stop surface 16 can be provided inlongitudinal member 2, as shown, by providing an enlarged portion of thelongitudinal member 2 next to washer seat portion 14.

Additional details of housing 3 of this embodiment are shown in FIGS. 24to 25. As previously described, housing 3 has a passageway 8 in itslateral edge 23 that is open between the top 24 of housing 3 and thebottom 25 of housing 3. Passageway 8 has sufficient width to accept theshank of a vertebral anchor. Housing 3 also has a bore 17 that ispreferably open between faces 21 and 22 of housing 3. Bore 17 is sizedto accept the frictional shoe 9 of longitudinal member 2, and bore 17 isopen to passageway 8 (FIGS. 19 or 20), such that the shaft of vertebralanchor “B” placed inside passageway 8 partially extends into bore 17.One face of housing 3 has a washer connection surface 19. Washerconnection surface 19 preferably includes structure for facilitating theengagement of housing 3 against rotational movement relative to the rodinterface washer 4 against which it is pressed. This engagementstructure is preferably a plurality of variable angle ridges 20 thatradiate from the axis 31 of bore 17.

In contrast to the previous embodiments of this invention and referringback to FIGS. 19 and 20, the reader may note the longer length offrictional shoe 9, the elongated shape of passageway 8, and the partialinternal taper of bore 17. Passageway 8 is elongated to provide foradjustable fixation of the vertebral anchor “B” along the length of shoe9. To assist in this result, it is preferable that lateral wall 34 ofpassageway 8 be tapered to complement the taper of inwardly tapered seatsurface 11 on shoe 9. Provided in this manner, substantially the sameamount of axial displacement of longitudinal member 2 from bore 17 willlock vertebral anchor “B” at any location inside passageway 8. Moreover,to minimize the amount of axial displacement required to lock vertebralanchor “B”, it is further preferable that side wall 35 also be taperedso as to push shoe 9 against vertebral anchor “B” when longitudinalmember 9 is axially displaced. And preferably, the taper inside wall 35is such that it too complements the taper of inwardly tapered seatsurface 11 as lateral wall 34 preferably does.

Yet another alternative embodiment of this invention is shown in FIG.27. In this embodiment, any of the foregoing connection assemblies 1 isused with an offset connector or spindle 35 and a compression member 36.Referring to FIG. 28, spindle 35 has a generally cylindrical projectionportion or shaft 37, a hole 30 for receiving a spinal implant rod, and athreaded opening 39 for receiving compression member 36. The length ofprojection portion 37 is preferably roughened or scored, as well as thewalls of hole 30. An example of such an offset connector or spindle iscommercially available as part of the LIBERTY™ system offered byMedtronic Sofamor Danek located in Memphis, Tennessee, U.S.A.

Instead of attaching connection assembly 1 directly to spinal implantrod “A”, spindle 35 is attached to rod “A” and secured by compressionmember 36. Connection assembly 1 is then secured to the offset connectorby inserting projection portion 37 into aperture 6 and tighteningconnector assembly 1 as previously described.

While the invention has been illustrated and described in detail, thisis to be considered illustrative and not restrictive of the patentrights. The reader should understand that only the preferred embodimentshave been presented and all changes and modifications that come withinthe spirit of the invention are included if the following claims or thelegal equivalent of these claims describes them.

What is claimed is:
 1. A connection assembly between a spinal implantrod and a vertebral anchor, the assembly comprising: (a) a longitudinalmember, said longitudinal member having a shoe disposed near one end ofthe longitudinal member and an aperture for receiving a portion of thespinal implant rod near the opposite end of the longitudinal member; (b)a housing, said housing having a first face, a second face, and alateral edge, said housing having a passageway opening to the lateraledge to receive a portion of the vertebral anchor, the passageway havingan internal wall, said housing having a bore opening to the first faceto receive at least a portion of the shoe of said longitudinal member,said housing being movable in part over at least a portion of the shoeof said longitudinal member, the passageway further open to the bore;(c) a rod interface washer, said rod interface washer positioned over aportion of the longitudinal member between the aperture of saidlongitudinal member and the first face of said housing, said rodinterface washer being movable in part between the aperture of saidlongitudinal member and said housing, said rod interface washer beingfixed against rotation relative to said longitudinal member; (d) acompression member, said compression member forceably engaged to saidlongitudinal member to urge the rod toward the vertebral anchor, wherebythe shoe will be moved in the bore to urge the vertebral anchor towardthe internal wall of the passageway in said housing, and whereby saidhousing and said rod interface washer will be pressed together.
 2. Theconnection assembly of claim 1, wherein the shoe of said longitudinalmember is a wedge.
 3. The connection assembly of claim 1, wherein theshoe of said longitudinal member has a round cross-section.
 4. Theconnection assembly of claim 1, wherein the shoe of said longitudinalmember is conical shaped.
 5. The connection assembly of claim 1, whereinthe shoe of said longitudinal has a convex taper.
 6. The connectionassembly of claim 1, wherein the shoe of said longitudinal member has aconcave taper.
 7. The connection assembly of claim 1, wherein the shoeof said longitudinal member has a substantially straight taper.
 8. Theconnection assembly of claim 1, wherein said housing and said rodinterface washer have interengagement structure on a surface such that,when pressed together, the interengagement structure will facilitateagainst rotational movement relative to one another.
 9. The connectionassembly of claim 1, wherein the shoe of said longitudinal member istapered and the shoe has a lateral edge.
 10. The connection assembly ofclaim 9, wherein the passageway is a slot and at least a portion of theinternal wall of the slot is substantially parallel with at least aportion of the lateral edge of the shoe of said longitudinal member. 11.The connection assembly of claim 9, wherein at least a portion of thebore in said housing is complementary tapered to mate with at least aportion of the taper of the shoe of said longitudinal member.
 12. Theconnection assembly of claim 9, wherein the shoe of said longitudinalmember has a substantially straight taper.
 13. The connection assemblyof claim 1, wherein the bore of said longitudinal member opens to thefirst face and the second face of said housing.
 14. A connectionassembly between a spinal implant rod and a vertebral anchor, theassembly comprising: (a) a spindle, said spindle having an aperture forreceiving a portion of the spinal implant rod, said spindle having aprojection portion; (b) a longitudinal member, said longitudinal memberhaving a shoe disposed near one end of the longitudinal member and anaperture for receiving a portion of the projection portion of saidspindle; (c) a housing, said housing having a first face, a second face,and a lateral edge, said housing having a passageway opening to thelateral edge to receive a portion of the vertebral anchor, thepassageway having an internal wall, said housing having a bore openingto the first face to receive at least a portion of the shoe of saidlongitudinal member, said housing being movable in part over at least aportion of the shoe of said longitudinal member, the passageway furtheropen to the bore; (d) a rod interface washer, said rod interface washerpositioned over a portion of the longitudinal member between theaperture of said longitudinal member and the first face of said housing,said rod interface washer being movable in part between the aperture ofsaid longitudinal member and said housing, said rod interface washerbeing fixed against rotation relative to said longitudinal member; (e) acompression member, said compression member forceably engaged to saidlongitudinal member to urge the rod toward the vertebral anchor, wherebythe shoe will be moved in the bore to urge the projection portion ofsaid spindle toward the internal wall of the passageway in said housing,and whereby said housing and said rod interface washer will be pressedtogether.
 15. The connection assembly of claim 14, wherein the shoe ofsaid longitudinal member is a wedge.
 16. The connection assembly ofclaim 14, wherein the shoe of said longitudinal member has a roundcross-section.
 17. The connection assembly of claim 14, wherein the shoeof said longitudinal member is conical shaped.
 18. The connectionassembly of claim 14, wherein the shoe of said longitudinal has a convextaper.
 19. The connection assembly of claim 14, wherein the shoe of saidlongitudinal member has a concave taper.
 20. The connection assembly ofclaim 14, wherein the shoe of said longitudinal member has asubstantially straight taper.
 21. The connection assembly of claim 14,wherein the shoe of said longitudinal member is tapered and the shoe hasa lateral edge.
 22. The connection assembly of claim 21, wherein thepassageway is a slot and at least a portion of the internal wall of theslot is substantially parallel with at least a portion of the lateraledge of the shoe of said longitudinal member.
 23. The connectionassembly of claim 21, wherein at least a portion of the bore in saidhousing is complementary tapered to mate with at least a portion of thetaper of the shoe of said longitudinal member.
 24. The connectionassembly of claim 21, wherein the shoe of said longitudinal member has asubstantially straight taper.
 25. The connection assembly of claim 14,wherein the bore of said longitudinal member opens to the first face andthe second face of said housing.